> Butt-candling[1] must work, just look all these happy customers!
But history is replete with ineffective or downright harmful treatments being popular long after the evidence showed them to be ineffective or harmful. Homeopathy is a prime example of this, seeing as those concoctions contain either no active ingredients or (in cases of low dilutions still labeled "homeopathic") contain ingredients picked based on notions of sympathetic magic ("like cures like").
[1] A hopefully fictional example.